Bronze coins were issued under the authority of the Senate while gold and silver was issued under imperial authority.
The inscription CONSTANTINVS IVN NOB C could be translated "Constantine the Younger, Noble Prince, Caesar." This coin was issued while Constantine was junior emperor (Caesar) under his father Constantine the Great, who was the senior emperor (Augustus).
As an aid in doing this I recommend Reading and Dating Roman Imperial Coins by Zander H.
His previous career was as a chemical engineer and during World War II his talents were used to make bombs and ammunition for our troops.
Many of his inventions were indeed inventions for which he applied for and received patents.
In setting out to write this article, I have the modest goal of helping new collectors of Roman Imperial coins to interpret the inscriptions on their coins.
I must state at the outset that there will be nothing new here, I travel the well marked path of the great numismatists who have gone before me. Reading and Dating Roman Imperial Coins by Zander Klawans has been the starting point for more Roman collectors than perhaps any other book of the last half century and the fact that it is still in print is a testament to it's value.